[llvm] [InstCombine] Use known bits to simplify mask in foldSelectICmpAnd (PR #128741)

[Julian Nagele via llvm-commits]

juliannagele wrote:

Thanks, I incorporated the code comments. For the alive proof did you have a specific generalization in mind? I'm not quite sure how to use/represent known bits and `isPowerOf2` there.

https://github.com/llvm/llvm-project/pull/128741